The present invention relates generally to a connector for maintaining the connection between electrical plugs and connectors and, in particular, to a plug lock for receiving an engaged plug and connector such as occurs when two electrical extension cords or a power cord from an appliance and an extension cord are joined together.
A portable electrical appliance such as a power saw, vacuum cleaner or the like is often used with an extension cord connected to the power cord of the appliance. It is not uncommon when using an electrical appliance connected to an extension cord that opposing forces along the axis of the cord cause the separation of the connection between the male and female plugs. This can be the result of one of the cords getting caught on an obstruction as the appliance is moved, the appliance being moved so that the cords are fully extended, or the appliance being used in an elevated location such that gravity pulls on the cord, for example.
Having the plugs separate completely is an annoying event; the user must stop whatever he is doing and restore the connection. Having the female and male plugs separate only partially is more than an annoyance. Electrically hot portions of the male plug can be exposed and cause electrical shocking or ignition of flammable material. In order to overcome these problems, a variety of plug clamps have been invented. For example, U.S. Pat. No. 3,609,638 describes a cord lock that is only adjustable if the connected cords are removed; U.S. Pat. No. 3,999,828 describes an adjustable device that uses friction for keeping the connected plugs together; and U.S. Pat. No. 4,664,463 uses a threaded adjustment device that keeps the connected plugs together.
The fact that the device described in U.S. Pat. No. 3,609,638 can only be adjusted when the connected cords are removed severely limits it usefulness. The device of U.S. Pat. No. 3,999,828 permits adjustment, but as the '828 device ages and the cords become coated with dirt and oil, for example, the '828 device's reliance on friction for keeping the connected plugs together is insufficient. The threaded adjustment device of U.S. Pat. No. 4,664,463 partially overcomes the deficiencies of the '638 and '828 devices. But the '463 device can only be manipulated slowly under ideal conditions (indoors or during warm weather) and could easily prove to be impossible to manipulate under adverse conditions (at cold temperatures for example).
Thus, it would be desirable to have a cord lock device that can be rapidly and easily adjusted yet will securely lock connected male and female plug ends in position.